PURPOSE: To compensate simply frequency fluctuation dependent upon the temperature of a piezo-oscillator, by providing a compensating circuit consisting of an induction element and the first diode and a compensating circuit consisting of a capacity element and the second diode in the piezo-oscillator.

CONSTITUTION: In the compensating circuit consisting of induction element 20 and the first diode 21, the impedance of diode 21 is increased to reduce the influence of the inductance of induction element 20 upon the reactance of crystal oscillator 16 by lowering of the terminal voltage of thermistor 22 dependent upon temperature rise in the low-temperature range, and thus, compensation in the low-temperature range is possible. In the compensating circuit consisting of capacity element 25 and the second diode 26, the impedance of diode 26 is reduced to enhance the influence of the reactance of capacity element 25 upon the reactance of crystal oscillator 16 by lowering of the terminal voltage of thermistor 22 dependent upon temperature rise in the high-temperature range, and thus, compensation in the high-temperature range is possible.